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The fine structure of four glioblastomas and two cerebellar astrocytomas maintained in organ culture systems up to 137 days and 43 days, respectively, using either a three-dimensional sponge foam matrix technic or a Millipore filter platform technic, is described and compared. The cells of both tumor types showed increased astrocytic differentiation, characterized by a progressive increase in glial filaments associated with an increase in free ribosomes and granular endoplasmic reticulum. A progressive increase in basement membrane material, presumably originating from explanted endothelial cells or pericytes, was also found in both tumor types and was often associated with increased numbers of collagen fibrils. Astrocytic tumor cell processes frequently preserved their contact with this basement membrane material. Microvascular fenestrations or gaps in endothelial cells were not identified. These electron microscopic features appear to correspond to the early stages of perivascular sclerosis previously noted by light microscopy in gliomas maintained in organ culture systems and are presumably related to the progressive obliteration of the functional microvasculature.

Light microscopy observations are described on five human glioblastomas grown in organ culture systems, using either a three-dimensional sponge foam matrix technic or a Millipore filter platform technic. Many cultures were successfully maintained for more than 2 months; one was maintained for 137 days. Invasion of the sponge foam matrix by glioma cells was invariably demonstrated. Mitotic figures were seen up to 122 days after explantation. All tumors showed the development of well-differentiated astrocytes; they often showed increased glial fibrillogenesis in the later stages of culture. Oligodendroglia were also demonstrated in one case. The in vivo features of pseudopalisading and endothelial proliferation were not seen. On the contrary, the vascular stroma of several explants showed a marked tendency to undergo sclerosis, with thickening, hyalinization and gradual obliteration of the vascular lumens. The cultural behavior of the explants with this technic was compared with that of sister cultures grown on collagen-coated coverslips. The organ culture technics revealed some important differences in growth characteristics. In contrast to what was seen in collagen-coated coverslip cultures, fibroblastic proliferation was inhibited, and the marked anaplastic cellular features that were sometimes manifest after 4 to 6 weeks on coated coverslips were not seen in the organ cultures.